Explain the encapsulated anonymous function syntax

Question

Summary

Can you explain the reasoning behind the syntax for encapsulated anonymous functions in JavaScript? Why does this work: (function(){})(); but

Answer 1

I have just another small remark. Your code will work with a small change:

var x = function(){
    alert(2 + 2);
}();

I use the above syntax instead of the more widely spread version:

var module = (function(){
    alert(2 + 2);
})();

because I didn't manage to get the indentation to work correctly for javascript files in vim. It seems that vim doesn't like the curly braces inside open parenthesis.